This disclosure relates to a ram air turbine (RAT) deployment system, and more particularly, the disclosure relates to an actuator for the system.
Ram Air Turbines (RATs) are utilized on numerous aircraft to provide hydraulic and electrical power in emergency situations. The RAT is stowed in the aircraft structure and deployed into the air stream by a deployment actuator. The deployment actuator is attached to aircraft structure and to an arm on the strut of the RAT. On deployment, the deployment actuator forces the RAT to rotate out of its stowed, or retracted, position in the aircraft and into the air stream. The air stream acts on the RAT blades to spin the turbine and governor assembly, which in turn operates an electrical generator and hydraulic pump providing power to the aircraft. The RAT is held in the aircraft by an up-lock mechanism and is restrained in the deployed position by a down-lock mechanism, both of which are contained within the deployment actuator.
Typical up-lock and down-lock mechanisms utilize locking wedges, which restrain the actuator in either the stowed or deployed position. Deploying the actuator when only limited electrical power is available in emergency cases is challenging. The loads on the actuator in a deployment scenario can become relatively high due to aircraft flight conditions. These emergency conditions can generate high door loads when attempting to push the RAT into the air stream in-flight. Various wedge arrangements have been used to lock the actuator into position in numerous actuators. In one example, four up-lock wedges are released by sliding the lock bolt across an inner diameter of the wedges such that the wedges drop into a groove in the lock bolt that then releases the actuator to deploy the RAT.
In another example hydraulic locking actuator, rollers are used between two wedges to reduce the amount of force required to move the lock bolt to release the actuator. But, the load that can be applied to the actuator is limited.